The Martial Arts in general do not add to your DB, but Martial Artists can purchase ranks in Adrenal Defense, which does work to boost their DB.
Not positive (i.e. my memory is faulty here) about the DB column or the Sw/Th column in the MA section of the sheet, but I would think that the Sw/Th column is there for making a check mark to indicate whether is is a Strikes or a Sweeps style of martial arts.
ictus created the sheet, and if I had to guess (since I cannot seem to remember at this point - hey! I have slept since then), I would think that those lines were basically added in regards to specific styles (i.e. Shaolin Tiger style versus Judo, if you wanted to get into that sort of detail (besides which the Combat Companion I am working on will actually include style creation rules for both MA and normal weapon styles.